Wireless power transfer using inductive coupling

Abstract

The present invention suppresses leakage magnetic field. A power transfer coil configured to transmit or receive power includes: an inner coil; a first outer coil formed so as to surround the inner coil such that a magnetic flux opposite in phase to a magnetic flux outside the inner coil is generated outside the first outer coil, the first outer coil having one end connected to a first terminal and the other end connected to one end of the inner coil; and a second outer coil formed so as to surround the inner coil such that a magnetic flux opposite in phase to the magnetic flux outside the inner coil is generated outside the second outer coil, the second outer coil having one end connected to a second terminal and the other end connected to the other end of the inner coil.

The invention claimed is: 
     
       1. A mobile communication apparatus comprising:
 a power receiving coil for receiving an electric power from an external apparatus; 
 a battery for reserving the electric power; 
 a communication circuitry for communicating with the external apparatus; 
 a controller configured to: 
 control charging the electric power to the battery, and 
 control the communication circuitry to detect a presence of the external apparatus; and 
 a power supply circuitry connected to the power receiving coil via a rectifier circuitry, the controller and the battery; 
 wherein the power receiving coil is comprising: 
 an inner coil having circular shape; 
 a first outer coil having circular shape formed so as to surround outside of the inner coil such that a magnetic flux opposite in phase to a magnetic flux outside the inner coil is generated outside the first outer coil, the first outer coil having one end connected to a first terminal and another end connected to one end of the inner coil; and 
 a second outer coil having circular shape formed so as to surround outside of the inner coil such that a magnetic flux opposite in phase to the magnetic flux outside the inner coil is generated outside the second coil, the second coil having one end connected to a second terminal and another end connected to another end of the inner coil, and 
 wherein the inner coil, the first outer coil and the second outer coil are each formed so as to be symmetrical when viewed from the one end of the first outer coil connected to the first terminal and the one end of the second outer coil connected to the second terminal. 
 
     
     
       2. The mobile communication apparatus according to  claim 1 ,
 wherein the first outer coil and the second outer coil have a same shape and are arranged at a same position. 
 
     
     
       3. The mobile communication apparatus according to  claim 1 ,
 wherein a current flowing in the inner coil is twice as large as a sum of a current flowing in the first outer coil and a current flowing in the second outer coil, and 
 a radius of the first outer coil and second outer coil is square root of two times as large as a radius of the inner coil. 
 
     
     
       4. The mobile communication apparatus according to  claim 1 ,
 wherein the power receiving coil is further comprising: 
 a first capacitor element connected between the inner coil and the first outer coil; and 
 a second capacitor element connected between the inner coil and the second outer coil. 
 
     
     
       5. The mobile communication apparatus according to  claim 1 ,
 wherein the controller is further configured to transmit information relating to charging level of the battery to the external apparatus via the communication circuitry. 
 
     
     
       6. The mobile communication apparatus according to  claim 1 ,
 wherein the controller is further configured to transmit information relating to the power receiving coil to the external apparatus via the communication circuitry. 
 
     
     
       7. A smartphone comprising:
 a power receiving coil for receiving an electric power from an external apparatus; 
 a battery for reserving the electric power; 
 a communication circuitry for communicating with the external apparatus; 
 a controller configured to: 
 control charging the electric power to the battery, and 
 control the communication circuitry to detect a presence of the external apparatus; and 
 a power supply circuitry connected to the power receiving coil via a rectifier circuitry, the controller and the battery; 
 wherein the power receiving coil is comprising: 
 an inner coil having circular shape; 
 a first outer coil having circular shape formed so as to surround outside of the inner coil such that a magnetic flux opposite in phase to a magnetic flux outside the inner coil is generated outside the first outer coil, the first outer coil having one end connected to a first terminal and another end connected to one end of the inner coil; and 
 a second outer coil having circular shape formed so as to surround outside of the inner coil such that a magnetic flux opposite in phase to the magnetic flux outside the inner coil is generated outside the second coil, the second coil having one end connected to a second terminal and another end connected to another end of the inner coil, and 
 wherein the inner coil, the first outer coil and the second outer coil are each formed so as to be symmetrical when viewed from the one end of the first outer coil connected to the first terminal and the one end of the second outer coil connected to the second terminal. 
 
     
     
       8. The smartphone according to  claim 7 ,
 wherein the first outer coil and the second outer coil have a same shape and are arranged at a same position. 
 
     
     
       9. The smartphone according to  claim 7 ,
 wherein a current flowing in the inner coil is twice as large as a sum of a current flowing in the first outer coil and a current flowing in the second outer coil, and 
 a radius of the first outer coil and second outer coil is square root of two times as large as a radius of the inner coil. 
 
     
     
       10. The smartphone according to  claim 7 ,
 wherein the power receiving coil is further comprising: 
 a first capacitor element connected between the inner coil and the first outer coil; and 
 a second capacitor element connected between the inner coil and the second outer coil. 
 
     
     
       11. The smartphone according to  claim 7 ,
 wherein the controller is further configured to transmit information relating to charging level of the battery to the external apparatus via the communication circuitry. 
 
     
     
       12. The smartphone according to  claim 7 ,
 wherein the controller is further configured to transmit information relating to the power receiving coil to the external apparatus via the communication circuitry. 
 
     
     
       13. A power transfer apparatus comprising:
 a power transfer coil for transmitting an electric power to an external communication apparatus; 
 a communication circuitry for communicating with the external communication apparatus; and 
 a controller configured to: 
 control transmitting the electric power to the external communication apparatus; and 
 control the communication circuitry of the power transfer apparatus to detect a presence of the external communication apparatus; and 
 wherein the power transfer coil is comprising: 
 an inner coil having circular shape; 
 a first outer coil having circular shape formed so as to surround outside of the inner coil such that a magnetic flux opposite in phase to a magnetic flux outside the inner coil is generated outside the first outer coil, the first outer coil having one end connected to a first terminal and another end connected to one end of the inner coil; and 
 a second outer coil having circular shape formed so as to surround outside of the inner coil such that a magnetic flux opposite in phase to the magnetic flux outside the inner coil is generated outside the second coil, the second coil having one end connected to a second terminal and another end connected to another end of the inner coil, and 
 wherein the inner coil, the first outer coil and the second outer coil are each formed so as to be symmetrical when viewed from the one end of the first outer coil connected to the first terminal and the one end of the second outer coil connected to the second terminal. 
 
     
     
       14. The power transfer apparatus according to  claim 13 ,
 wherein the first outer coil and the second outer coil have a same shape and are arranged at a same position. 
 
     
     
       15. The power transfer apparatus according to  claim 13 ,
 wherein a current flowing in the inner coil is twice as large as a sum of a current flowing in the first outer coil and a current flowing in the second outer coil, and 
 a radius of the first outer coil and second outer coil is square root of two times as large as a radius of the inner coil. 
 
     
     
       16. The power transfer apparatus according to  claim 13 ,
 wherein the power transfer coil is further comprising: 
 a first capacitor element connected between the inner coil and the first outer coil; and 
 a second capacitor element connected between the inner coil and the second outer coil. 
 
     
     
       17. The power transfer apparatus according to  claim 13 ,
 wherein the controller is further configured to receive information relating to charging level of a battery of the external communication apparatus from the external communication apparatus via the communication circuitry. 
 
     
     
       18. The power transfer apparatus according to  claim 17 ,
 further comprising a display, 
 wherein the controller is further configured to display the charging level of the battery of the external communication apparatus on the display. 
 
     
     
       19. The power transfer apparatus according to  claim 13 ,
 wherein the controller is further configured to receive information relating to a power receiving coil of the external communication apparatus from the external communication apparatus via the communication circuitry. 
 
     
     
       20. The power transfer apparatus according to  claim 19 ,
 further comprising a display, 
 wherein the controller is further configured to display a dialog screen on the display based on the received information relating to the power receiving coil of the external communication apparatus.